重建二叉树(important!)

题目描述
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

python solution:

# -*- coding:utf-8 -*-
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    # 返回构造的TreeNode根节点
    def reConstructBinaryTree(self, pre, tin):
        if not pre or not tin:
            return None
        root = TreeNode(pre.pop(0))
        pos = tin.index(root.val)
        root.left = self.reConstructBinaryTree(pre,tin[:pos])
        root.right = self.reConstructBinaryTree(pre,tin[pos+1:])
        return root